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It is the branch of biology which deals with the study of interaction of living organisms with their environment.

It the place where living organisms live.

It is sum of number of individuals of same specie.

A group of different species of plants and animals living in a same area is called community.

This method is common in animals. In this case new organisms move in to the habitat and share with the existing organisms thus causing increase in population size of the animals.

These are already existing organisms in the habitat which have similar requirements and eat the same food.

There are organisms already present in the habitat which feed on new comers.

The organisms along with their environment form an ecosystem. There are two factors or components of ecosystem.

1. Biotic
2. Abiotic

There are non-living components of ecosystem. Following are important abiotic components.

All the metabolic reactions take place at optimum temperature. So living organisms need specific range of temperature for normal activities.

It is very important factor. It constitutes about 75-85% of the protoplasm.

Soil provide water and minerals needed by the organisms of the ecosystem. Potassium, calcium, phosphorus, nitrogen and other are needed for the growth of organisms. Soil is composed of inorganic matter produced by mechanical weathering of rocks.

Atmosphere is vital part of the ecosystem. It is reservoir of carbon dioxide and oxygen required for photosynthesis and respiration.

It is the source of energy for all ecosystem. During photosynthesis plant change light energy to chemical energy, subsequently used by all living things.

Biotic components are three types viz. Producers, consumers and decomposers.

Green plants are known as producers because they synthesize their own food. These green plants are source of food for other living organisms of ecosystem.

Living organisms which cannot manufacture their food and take prepared food from their environment are called consumers. Following are the types of consumers.

Those organisms which directly feed on plants are called primary consumers. Such animals are called herbivores animals.

Carnivores animals depend for food on primary consumers are called secondary consumers.

Those animals which feed on secondary consumers are called tertiary consumers.

Bacteria and fungi are included in this group. They are saprophytic and decompose dead organic matter.

The transfer of food energy from its basic source (plants) through series of organisms (primary, secondary and tertiary consumers) and ultimately to the decomposers is called food chain.

• Producers® Primary consumers® Secondary consumers®

Tertiary consumers ® Decomposers

• Grass® Grass hopper® Lizard® Hawk
• Grass® Cow® Human

Many food chains unit to form food web. The alternative pathways in food web help in maintaining the stability of the ecosystem.

The cyclic flow of chemical elements from non-living environment to living organisms and from living organisms to non-living environment. Producers make food by the process of photosynthesis. This food is passed through series of consumers to decomposers. Decomposers convert the complex form to their simpler element form.

The light and heat energy from sun is obtained and transferred to the chemical energy by producers. Producers does not absorb all energy. Part of energy is lost by them. From producers energy is transferred to primary consumers during this transfer part of energy is also lost. In this way this chemical energy is transformed to tertiary consumers and decomposers.

Ecological or biological pyramid is used to express relationship of producers and consumers. At the base of pyramid there are producers or green plants. The upper levels are occupied by primary, secondary and tertiary consumers. The pyramid may be based on the number, weight or size.

It is the equilibrium maintained by an ecosystem between plants and animals and their non living environment is called balance in nature.

The cyclic flow of water to its various reservoirs. The water on earth changes into vapours and condense to form clouds. These clouds precipitates and as the result rain falls on earth. Some of the water vapours are contributed by animals (by respiration) and by plants (transpiration) into the atmosphere.

Animals take oxygen from atmosphere and release CO₂. The CO₂ produced during respiration is utilized during photosynthesis. During night there is no photosynthesis so only CO₂ is produced and oxygen is used by the plants.

Green plants photosynthesize CO₂ into sugar. Most other organic molecules are made using sugar e.g., cellulose, protein etc. When these are eaten by animals the digested products are turned into animals carbohydrates, fats and proteins.

This variety of organic molecules is returned to air as CO₂ during respiration in living organisms, or by combustion of fuels.

Fuels include wood and the fossil fuels coal and petroleum and natural gas.

Green plants need nitrates for protein synthesis. Nitrates are available to green plants from four sources:

e.g., ammonia nitrate.

Cause formation of oxides of nitrogen.

Convert atmospheric nitrogen into nitrates.

Oxidized ammonia compounds to nitrites and then nitrates.

Nitrates are turned into nitrogen gas by denitrifying bacteria if soil lack air as in water logged conditions. Nitrogen gas is useless for green plants.

Green plants form amino acids from nitrates. Proteins are made form amino acids. Animal convert protein to their own, but in doing so waste source e.g., urea and uric acid which is excreted.

Decomposers break dead organisms and their waste.

It is defined as undesirable changes in natural environment.

Following are the types of pollution:

1. Water pollution
2. Air pollution
3. Soil pollution
4. Noise pollution

Following are the important causes of water pollution.

Many microorganisms grow in water and make it harmful for living organisms.

Artificial fertilizers and pesticides are used in agriculture. They make water impure.

Industrial waste products are disposed in water which make it impure.

Sewage is discharge in river water, which produces impurities in water.

Following are important causes of air pollution.

They produce many gases like carbon monoxide and lead compounds.

Industries produce many poisonous gases like nitrogen oxides, carbon monoxide and lead compounds.

Radiations like a , b , g and x - rays are produced by some machines. These radiations produce harmful effect on environment.

Plastic, polyethene bags, sewage garbage and many other factors are responsible for soil pollution. These factors decrease the fertility of the soil.

Noise is an unpleasant sound. Noise pollution is due to industries, automobiles, air planes, trains, ships etc.

A green house is a place constructed to provide stable warmer environment for plants to accelerate their growth. Its roof and walls are made up of plastic which allow the sun heat to enter the house.

In nature there are certain gases in atmosphere (like carbon dioxide) which serve like plastic sheets. As the result certain amount of heat energy is retained in the atmosphere producing warming effect on the earth which is green house effect.

There is a layer of ozone around the earth. Ozone layer reflect the ultraviolet rays coming from the sun. If these rays come to the atmosphere they can cause skin cancer. In these days the chlorofluoro compounds produced by industries are destroying this layer which is a serious problem.

The term wild life includes all the plants and animals. Each individual specie has specific role in its environment. Conservation of wild life is essential to save successful species.

Plantation and management of forest is called forestry.

Following are the advantages of forests.

1. Forests make atmosphere cool by transpiration.
2. They are source of food.
3. Honey is obtained from the forest.
4. Number of species of animals live in forest.
5. Forests yield wood which is used for manufacturing furniture, sports good, buildings, paper etc.
6. Forest prevent soil erosion.

It is very useful insect which lives in colonial form. It produce wax and honey. Honey is used in medicine and dietary products.

It is natural source of silk. Silk fibers are obtained from the pupae of silk worm. Fabric are made from these fibers.

The products of dairy farms are milk, butter, cheese, ghee etc. These products are obtained from the milk of cattles (cow, goat). Milk is treated or passed with some processes to make it pure.

Birds are important sources of food. Eggs and white meat is obtained from poultry farms. Eggs and meat contain high class protein.

Fish is highly nutritive food. It is the science of production of fishes under controlled conditions. Fishes are found in ponds, streams, lakes, rivers and oceans. Some most important fishes are Herring, Salmon, Cods, Cat fish, White fish and Trout.

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